<!DOCTYPE html>
<style>
#animated {
  width: 100px;
  height: 100px;
  background: blue;
  opacity: 1;
  transition: opacity 1000s;
}
</style>
<div id="animated"></div>
<script>
onload = function() {
  animated.style.opacity = "0";
  if (window.internals)
    internals.forceCompositingUpdate(document);
  parent.postMessage("done", "*");
};
</script>
